Flexible fabric container and method of making same

ABSTRACT

A method of making an improved flexible crash resistant fabric container, the building steps comprising coating the fabric with an elastomeric material without obtaining penetration of the elastomeric material into the interstices of the fabric and plying up the fabric over the building form, wherein the seams are placed at least one inch away from corners and the other seams in the multiplied construction and the seam area is formed by overlapping at least one inch.

United States Patent Musyt et al. [4 1 Nov. 21, 1972 [54] FLEXIBLE FABRIC CONTAINER AND 2,621,142 12/1952 Wetherell ..53/32 X METHOD OF MAKING SAME 2,620,964 12/1952 Rose et al. ..53/32 X 721 Inventors: William Musyt, 1311 Brittain Road, ga 3 g 4/1940 "53/32 x Akron, Ohio 44310; James 9, 68 5/1955 Kainbonan ..156/475 X Tremelin, 490 M cpherso n Avenue, 2,844,178 7/1958 Co eman ..150/0.5 Akron Ohio 44313 3,492,393 1/1970 Nourot et al. ..264/279 [22] Filed: Dec. 22, 1969 Primary Examiner-Benjamin A. Borchelt Assistant Examiner-Gregory E. Montone [21] Appl. No.. 887,178 Attorney-F. W. Brunner and J. D. Wolfe [52] US. Cl. ..150/0.5, 156/212, 156/213, [57] ABSTRACT [51] Int Cl g figg A method of making an improved flexible crash re- [58] Fie'ld 53/32 sistant fabric container, the building steps comprising 53/2191 7 150/ coating the fabric with an elastomeric material without obtaining penetration of the elastomeric material into the interstices of the fabric and plying up [56] References Cited the fabric over the building form, wherein the seams UNITED STATES PATENTS aria1 placed at leasth one inlch lawiy from corners an; the ot er seams 1n t e mu tip 1e construction an t e l; ai l f seam area is formed by overlapping at least one inch. o 2,979,871 4/ 1961 Kieckhefer ..5 3/32 X 3 Claims, 6 Drawing Figures 22 I ,p/ i I PATENTEI'JIwm 1912 3.703201 24 23 INVENTORS WILLIAM MUSYT BY JAMES D.TREMELIN ATTORNEY FLEXIBLE FABRIC CONTAINER AND METHOD OF MAKING SAME This invention relates to the method of constructing containers such as fuel cells and to said containers. More specifically, this invention relates to a method of constructing a crash-worthy fuel cell, specifically, an impact-resistant container of the flexible walled rupture-resistant, fluid-impervious type.

Fuel cells have been constructed of rubberized fabric plied up over a building form since at least World War I and extensive effort and research has been devoted to the problem of attempting to produce a fuel tank that would survive a crash which would not be of sufficient severity to kill the passenger upon impact. The need for such an impact-resistant container has resulted in many proposed solutions, but these have required use of excess material with its corresponding weight problem.

An object of this invention is to provide a method of constructing a rubberized fabric container such as a fuel cell that is impact and rupture resistant to reduce loss of fluid when the container is subjected to impact or crash conditions.

This object and other advantages of this invention can more readily be understood and appreciated by reference to the drawings wherein:

FIG. 1 is a perspective view of a fuel cell building form containing a rubberized fabric draped thereon.

FIG. 2 is a perspective view showing the rubberized fabric draped on the form of FIG. 1 cut and seamed to give a drape corresponding to the dimensions of the form.

FIG. 3 is an inverted view of FIG. 2 containing another rubberized fabric draped thereon.

FIG. 4 is a picture of the finished fuel cell.

FIG. 5 is a cross section through FIG. 4 along the lines 5-5.

FIG. 6 is an enlarged partial view in broken section showing the relationship of the seams in each ply to the seams in the adjacent plies.

Referring specifically to FIG. 1, it will be noted that numeral 10 refers generally to a fuel cell building form which may be of any conventional construction such as plaster of paris, cardboard, etc. Draped over the top of the form 10 is a rubberized fabric 11. It should be noted that this fabric is draped over the form and is hanging loosely thereon in the manner frequently referred to as a tablecloth drape. Thus, it will be noted that at each of the corners 12 the cloth tends to bulge out and does not drape down smoothly along the sides of the mold.

Then, referring to FIG. 2, it will be noted that these bulging corners 12 have been cut along the lines 13 and 14 to remove a V-shaped gore from cloth in the vicinity of edge 15 to be specific, and then this cloth where the gore has been cut out was lapped over to form the seamed area 16 which can be treated with a suitable cement or the natural adhesives of the rubberized fabric can be used to adhere the lapped portions together when they are pressed down smoothly against the form to give a corner that tightly fits to the mold around edge 15, as shown in FIG. 2. Likewise, the cloth at the other three edges are cut to remove a gore and to form a seam in the vicinity of each of the edges and corresponding corners wherein the seam is no closer to any edge than 1 inch and preferably to about 2 inches, and the overlap in the seam is at least 1% inch, and preferably about 2 inches.

All four corners of the cloth, spread over the form in a tablecloth manner, are cut and seamed to give a tight fit at each edge 15, 17, 18 and 19 respectively. Then the form is ready to be inverted and have a second rubberized fabric displayed thereon in the normal tablecloth drape as best shown in FIG. 3.

It should be noted that one of the aspects of this invention is that the second piece 20 of rubberized fabric draped over the mold extends at least 1% inches, and preferably 2 or more inches, below the edge 21 of the first piece of cloth draped over the mold as shown in FIGS. 1 and 2. Then the second piece of cloth 20 is cut at each corner to form a gore in the cloth with the requirement that when the gore is cut in the cloth and the pieces overlapped to form the seam 22, shown in FIG. 4, that no seam will be closer than 1 inch and preferably about 1% to 2 inches to any edge and the overlap of the two pieces where the gore has been removed will be at least 1% inches and preferably about 2 inches. In forming these seams suitable cements can be added to assure proper adhesion thereto, rather than use the natural adhesiveness of the rubberized fabric.

Thus, with the form totally enclosed in a rubberized fabric, as shown in FIG. 4, then additional layers of fabric may be applied to give a finished construction such as best seen and understood by reference to FIGS. 5 and 6.

It is a necessary feature of this invention that when the next ply of rubberized fabric is applied over the preceding ply that the seams be staggered in the manner best seen in FIG. 6. Thus, with the first ply 35 laid up over the mold to form seam 36 the second ply 37 is laid over ply 35 to give a seam 38 in ply 37 that is at least 1% inches and preferably 2 inches from seam 36. Likewise, ply 39 is laid up over ply 37 to have its seam 40 displaced a like distance from the seams 36 and 38 respectively of plies 35 and 37 and from the seam 41 of the next successive ply 42.

Thus, it is a necessary requirement that each seam in adjacent plies be displaced from each edge and each adjacent seam by at least 1% inches, and preferably 2 inches.

Another feature of this invention is the use of a tie strip over those seams that lie within about 2 inches or less of any edge or comer. Also, tie strips over the seams formed by placing fittings within the container in the conventional manner are very desirable and beneficial to help distribute the high stresses imparted to the tank by said fittings on crash.

In FIG. 5 numeral 23 indicates an innerliner coat that has been applied over the mold prior to the time the rubberized fabric was draped and cut to form the edge seam as discussed heretofore in regard to FIGS. 1, 2, 3 and 4. This innerliner 23 preferably is a coating of a liquid polyurethane reaction mixture which reacts to give a flexible tough polyurethane coating over the mold. Usually, this coating is about 1 to 15 mils in thickness and the innerliner is followed usually and preferably by a barrier coat 24 to seal the fuel cell against the loss of fuel by penetration thereof through the wall of the container. This barrier may be applied either by spraying, dipping, painting, or the other wellknown methods of applying barrier coats to fuel cells. Likewise, the barrier may be nylon, vinylidene chloride or any of the other materials well-known to the art.

Vinylidene chloride in a suitable solvent such as mixtures of 40-70 percent methyl ethyl ketone to 60-30 percent toluene is preferred as it may be applied by spray coating and is not subjected to some of the defects and difficulties experienced when using nylon. Normally, a cover coat 25 is applied over the barrier coat to protect the barrier coat from scuffing and abrasion. This cover coat preferably is applied by spraying, dipping or otherwise coating the barrier with a liquid polyurethane reaction mixture and then reacting to give a cover coat of polyurethane. Over the cover coat 25 is applied a tie ply or coat. The tie ply coat applied as a first ply 26 in FIG. 5 was a medium modulus acrylonitrile butadiene rubber in a suitable solvent and containing about 25-50 parts of phenol formaldehyde resin per hundred parts of the acrylonitrile butadiene elastomer. Then over the tie ply coating 26 there was applied an additional tie ply coating 27. Preferably this is a low modulus high tack acrylonitrile butadiene elastomer which contains about 40-70 parts of phenol formaldehyde resin per hundred parts of elastomer.

Numeral 28 in FIG. 5 represents the first rubberized fabric coating applied over the mold in the manner described heretofore in regard to FIGS. 1, 2, 3 and 4 wherein a first fabric 11 was draped over the mold and then was followed in due course by a second fabric which was draped over the mold from the opposite end. This initial coating or covering 28 of fabric is then followed by a second covering of fabric 29 which is applied in a manner analagous to that described heretofore in applying and seaming the tablecloth drape of the cloths 11 and 20. Then, depending on the weight and the strength of the fabric used, additional coats of fabric 30 and 31 may be applied over the first coats 28 and 29 to give the finished container which may contain a tie ply coat 32 which may be of a nature similar to that described in regard to the tie plies enumerated as 26 and 27. Then over the tie ply coat 32 is applied a scuff coat 33. This scuff coat preferably is a polyurethane.

Any of the liquid polyurethane reaction mixtures can be used to apply coats 23, 24 and 33, depending on the use to which the container is to be subjected. A preferred liquid polyurethane reaction mixture is described in US. Patent application Ser. No. 763,945, filed Sept. 30, 1968, where the container is to be used in hot, humid climates to handle fuels. Also, the ones described in US. Patent application, Ser. No. 324,884, filed Nov. 19, 1963, are desirable where low temperature conditions exist.

The preferred material for construction of the containers are any of the high strength fabrics with those most generally used being polyester and nylon.

The nature of this invention is illustrated more clearly by the representative examples following, where all percentages and parts are by weight unless otherwise indicated.

EXAMPLE I prepared by the reaction of 4 moles of 4,4 -dicyclohexyl methane diisocyanate with a mixture of 1 mole of polytetramethylene adipate of 1,000 molecular weight and 1 mole of polytetramethylene adipate of 2,000 molecular weight. This liquid polyurethane reaction mixture was used to spray coat an aircraft fuel cell mold to give a coating of about 10 mils. A barrier coat of 2-3 mils comprising vinylidene chloride dissolved in methyl ethyl ketone and toluene was applied over the coating of polyurethane and this was followed by a coating of polyurethane of 6-8 mils thick over the barrier coat.

A tie coat of about 1-2 mils was applied over the polyurethane coating on the barrier coat. This tie coat had the following composition:

and a sufficient amount of the 50/50 mixture of toluene and methyl ethyl ketone to permit the tie coat to be painted on to the desired thickness.

Then a rubberized square woven nylon fabric with a weight of 12 ounces per square yard, having 3 i 0.5 ounces per square yard of butadiene acrylonitrile rubber per side of fabric scrape coated thereon was applied over the tie coat, cut and seamed to give a covering where no seams were closer than 1 inch to an edge, with at least 1% inches of overlap in the seam area. The rubberized fabric was added to give 3 plies of fabric in the container. A tie coat of about 1 mil was applied over the last ply of rubberized fabric and then a scuff coat of about 6 mils of the liquid polyurethane reaction mixture was applied. The finished container was cured in a hot air pressure autoclave for 1 hour at 225 F. at pounds per square inch (p.s.i.) and three and onehalf hours at 240 F. at 60 p.s.i. Then it was allowed to cool for 1 hour at 60 p.s.i. before being removed from the autoclave.

The term scrape coat is used in its normal usage in the spread coating art to indicate the dough or cement was spread on the cloth to coat the surface of the cloth with no penetration (normally no more than about 1 mil) of the interstices of cloth as is obtained in a body sprea operation. A satisfactory dough for scrape coating the fabric is shown in the following recipe:

Compound Parts 67/33 Butadiene acrylonitrile rubber 5!.35 Sulfur .90 Zinc oxide 2.57 Calcium silicate 15.40 Stearic acid .52 Dibutyl sebacate 12.84 Benzothiazyl disulfide 1.02 Durez Resin No. 12362 5.14 Coumarine lndene Resin 10.27 Methyl ethyl ketone 2 36 Another fuel cell was prepared according to the procedure of Example I using a l2-ounce per square yard nylon cloth having a 2 X 2 basket weave, a denier of 1,050/1, a thread count of 40 X 40 per inch and a producers twist. The cloth had a tensile of 650 pounds minimum on a l-inch level strip. This cloth was subjected to a standard RF tire cord predip treatment before being scrape-coated with 3 ounces of a polybutadiene acrylonitrile per square yard on each face of the cloth. The scrape treatment or coating of the fabric gives an adhesion preferably of about 3 to 6 pounds per square inch and no higher than 10 pounds per square inch of peel. This fabric was plied up over a polytetramethyladipate methane diphenylene diisocyanate-methylene-bis-ortho chloroaniline-type polyurethane coating on the building form. The polyurethane coating was about 10 to 30 mils thick with a polyvinyl-chloride barrier layer therein. The resulting fuel container having 4 plies of this nylon fabric and a scuff coating of polyurethane, when tested by MlL-T-2 7422B specification accordingto paragraphs 4.6151,

4.6.5.2, 4.6.5.3, and l.6. 6.2, gave a constant tear value and hydrocarbon polyols. Representative examples of the polyester polyols are those formed by the reaction of dicarboxylic or higher acids of two to about 20 and preferably about four to about 12 carbon atoms either 5 aromatic, aliphatic or alicyclic, with a polyol having of at least 400 foot-pounds, an impact penetration resistance of 75 foot-pounds, an impact tear resistance of at least 100 foot-pounds and a crash impact equivalent to a free-fall of at least 65 feet.

Thus, the use of a low modulus elastomer, preferably 200 to 400 pounds per square inch at 300 percent elongation, is preferred as it will allow the plies forming the I elastomeric covered fabric units nesting within each other to separate under severe impact conditions to relieve the stresses, especially where the coating on the fabric does not penetrate the fabric interstices and the individual yard or filaments can shift under the stress. It is preferred that the fabric be coated both inside and outside with the low modulus elastomer.

Although several plies can be used, it is desirable to reduce the number of plies as this reduces the labor in building the container. For instance, 4 plies of 12- ounce per square yard of fabric are satisfactory; economy of construction is achieved by using 2 or 3 plies such as 2 plies of 24-ounce per square yard of a nylon or polyester fabric.

In regard to coating the fabric with the elastomeric material, it should be indicated that the coatings are preferably built up from a cement by a scrape coating operation on a cement spreader, but it is possible to apply the elastomeric coating on the fabric by other means. For example, by spraying the fabric with a solvent solution of a polyurethane reaction mixture wherein the amount of solvent is adjusted to reduce or prevent the penetration of the spray coat into the interstices of the fabric and thereby permit the individual yarn or cords to move under strain. Any of the liquid polyurethane reaction mixtures that yield elastomers may be utilized in building up the elastomeric coatings on the building form or coating the fabric where desired. For instance, a reactive hydrogen containing polymeric material of at least 700 molecular weight can be reacted with an organic polyisocyanate and suitable cross-linking agents to form the polyurethanes useful in this invention.

Representative classes of reactive hydrogen containing materials are polyester polyols, polyether polyols,

from two to about 10 carbon atoms and containing from 2 up to 3, 4, 5 and even 8 hydroxyl groups. Representative of the polyether polyols are those formed by the condensation of an alkylene oxide of 2 to about 10 carbons on a cogeneric nucleus material such as the above-enumerated polyols and organic poly acids and amines.

Although this invention has been specifically exemplified by use of a prerubberized fabric and a spray coat of polyurethane on the building form, it should be appreciated that the spray coat of polyurethane on the building form can be replaced by a conventional rubber panel, viz. a polybutadiene acrylonitrile rubber, which is hand-laid up and seamed in the conventional manner. Likewise the scraped coated fabric can be replaced with uncoated fabric and then the fabric is coated by spray or paint coating, provided the interstices are not plugged to restrict movement of the individual yarns or cords.

Also, if desired, sealant layers may be used to afford bullet sealing qualities to the tank in the event the tank is penetrated with a bullet to allow fuel to contact the sealant layer. The sealant layer may be of conventional construction, for instance, a low cured natural rubber which swells in contact with the fuel to seal the puncture.

While certain representative embodiments and details have been shown for the purpose of illustrating 5 the invention, it will be apparent to those skilled in this art that various changes and modifications may be made therein without departing from the spirit or scope of the invention.

What is claimed is:

1. An impact-resistant container comprising a flexible walled rupture-resistant, fluid-impervious body portion, said body portion being composed of at least two elastomeric covered fabric units held in nesting relationship by the elastomer that bonds the fabric of each unit together but the elastomer does not penetrate the interstices of the fabric sufficiently to prevent the movement of individual yarns or cords of the woven fabric under conditions of impact to thereby distribute the load on the said units, the units being composed of panels of fabric seamed together to give a lapped seam of at least one inch with each seam being located at least one inch from any other seam and any edge of the container.

2. In the method of manufacturing impact resistant fuel containers having a body portion with fittings and corners, the step of forming an elastomeric layer of said body portion, laying up sufficient fabric panels over the elastomeric layer to form at least one overlapping seam per ply and at least two plies of said body potion, the improvement wherein the panels of each overlaps at 'least 1 inch to form said seam and each seam is positioned at least one inch from any other seam in said container and from the edge of the container, and the elastomeric coating on the fabric laid up being a surface coating with the penetration of the interstices being limited to permit the individual yarn to move under impact.

elastomer.

ion 

1. An impact-resistant container comprising a flexible walled rupture-resistant, fluid-impervious body portion, said body portion being composed of at least two elastomeric covered fabric units held in nesting relationship by the elastomer that bonds the fabric of each unit together but the elastomer does not penetrate the interstices of the fabric sufficiently to prevent the movement of individual yarns or cords of the woven fabric under conditions of impact to thereby distribute the load on the said units, the units being composed of panels of fabric seamed together to give a lapped seam of at least one inch with each seam being located at least one inch from any other seam and any edge of the container.
 2. In the method of manufacturing impact resistant fuel containers having a body portion with fittings and corners, the step of forming an elastomeric layer of said body portion, laying up sufficient fabric panels over the elastomeric layer to form at least one overlapping seam per ply and at least two plies of said body potion, the improvement wherein the panels of each overlaps at least 1 inch to form said seam and each seam is positioned at least one inch from any other seam in said container and from the edge of the container, and the elastomeric coating on the fabric laid up being a surface coating with the penetration of the interstices being limited to permit the individual yarn to move under impact. 